The present invention relates to the field of cages for bearings, in particular cages made of synthetic material used in ball bearings, notably with a deep race, in order to ensure the appropriate circumferential spacing between the balls. The invention also relates to bearing cages designed for high-speed operation.
Such types of cages have a generally annular shape with spherical recesses in which the balls are partially housed. The balls are retained in the recesses by clamps placed in pairs opposite to the heel of the cage. The spherical recesses have a diameter that is very slightly greater than that of the balls, so that a certain functional clearance exists between the halls and the recesses.
Document JP 2003-035 317 (NSK) or patent application US 2002/114550 describe a cage provided, between two recesses, with a deep groove extending from a radial face opposite to the clamps to the vicinity of the clamps. Notches are provided from the groove to the bore of the cage.
U.S. Pat. No. 4,938,613 and patent application JP 2005-514259 describe cages of constant thickness.
When the bearing rotates at high speed, under the effect of centrifugal force, the cage is subjected to stresses which tend to deform said cage, mainly in the radial direction, and shape it like an umbrella, that is to say give the cage a conical shape by increasing the diameter on the side of the clamps. Such deformations have consequences that are harmful to the correct operation of the bearing. Specifically, the edges of the recesses tighten against the balls, causing an increase in the friction torque and a scraping effect of the lubricant, rapidly leading to an accelerated degradation of the lubrication conditions of the bearing. There is also a risk of the ends of the clamps coming into contact with the bore of the outer race of the bearing, risking causing excessive wear of the cage.
Moreover, because of the high rotation speeds to which the bearing is subjected, the grease tends to be centrifuged outward into zones where it tends to stagnate or where the grease contributes only very little to the effective lubrication of the balls.